Question

\(5x^3-2x^2-7x=0\)

Giải pt

Answer 1

\(\Leftrightarrow x\left(5x^2-7x+5x-7\right)=0\\ \Leftrightarrow x\left[5x\left(x+1\right)+7\left(x+1\right)\right]=0\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x+1=0\\5x-7=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-1\\x=\dfrac{7}{5}\end{matrix}\right.\)

Answer 2

\(\Leftrightarrow5x^3+5x^2-7x^2-7x=0\)

\(\Leftrightarrow5x^2\left(x+1\right)-7x\left(x+1\right)=0\)

\(\Leftrightarrow\left(x+1\right)\left(5x^2-7x\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-1\\5x^2-7x=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-1\\x=0\\x=\dfrac{7}{5}\end{matrix}\right.\)